SALT LAKE CITY (AP) -- NASA scientists are studying autistic savant Kim Peek, hoping that technology used to study the effects of space travel on the brain will help explain his mental capabilities.

Last week, researchers had Peek -- who was the basis for Dustin Hoffman's character in the 1988 film "Rain Man'' -- undergo a series of tests including computerized tomography and magnetic resonance imaging, the results of which will be melded to create a three-dimensional look at his brain structure.

The researchers want to compare a series of MRI images taken in 1988 by Dr. Dan Christensen, Peek's neuropsychiatrist at the University of Utah, to see what has since changed within his brain.

Not only are Peek's brain and his abilities unique, noted Richard D. Boyle, director of the California center performing the scans, but that he seems to be getting smarter in his specialty areas as he ages is unexpected.

The 53-year-old Peek is called a "mega-savant" because he is a genius in about 15 different subjects, from history and literature and geography to numbers, sports, music and dates. But he also is severely limited in other ways, like not being able to find the silverware drawer at home or dressing himself.

"The goal is to measure what happens in Kim's brain when he expresses things and when he thinks about them,'' said his father, Fran.

He came to the attention of NASA researchers at the Center for Bioinformatics Space Life Sciences at the NASA-AMES Research Center when he spoke in late October at a Rotary Club in central California.

When Kim Peek was born, doctors found a water blister on the right side of his skull, similar to hydrocephalus. Later tests showed his brain hemispheres are not separated, forming a single, large ''data storage'' area.

It is likely that is why Peek has been able to memorize more than 9,000 books, his father said.

But he has lagged in other areas; his motor skills developed more slowly than those of his peers.

Fran Peek doesn't need the test results to know much has changed for his son in the last 16 years.

He was a shy young man with few social skills when the movie propelled him to public notice. But now, after speaking to more than two million people over the years, his father says he become calmer and is more at ease speaking in front of people.

He also no longer reads only nonfiction, Fran Peek said, but has dabbled with some fiction, such as books by Stephen King, because that is what so many people talk about.

When he's home in Utah, Peek spends afternoons at the Salt Lake City Public Library poring over books, even memorizing phone books and the Cole's address directory.

Kim Peek was the model author Barrow Morrow used for the original "Rain Man" script and screenplay, but the final product retained only a small part of the original story.